FIRES, FIREFIGHTING, AND EXPLOSIONS

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FIRES, FIREFIGHTING, AND EXPLOSIONS

• MSHA 2205
• November 1981
• June 2005

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Northern Mine Rescue Association
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INTRODUCTION

• Fighting a mine fire may be one of the most
  frequent duties that you perform as a rescue
  team. Fires in underground mines are particularly
  hazardous not only because they produce toxic
  gases and heat, but also because they produce
  smoke, pose an explosion hazard, and create
  oxygen-deficient atmospheres.
• In this module we'll talk about fire and
  explosions in the mine - how they occur and how
  they affect your job as a mine rescue team.

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Objective 1

• The team members will identify the components and
  meaning of the fire triangle

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FIRES

• Most fires are the result of a chemical reaction
  between a fuel and the oxygen in the air.
  Material such as wood, gas, oil, grease, and many
  plastics will burn when ignited in the presence
  of air. In each case, three elements are needed
  at the same time for the fire to occur fuel,
  oxygen, and heat (which is initially provided by
  the ignition source).
• The "fire triangle" can be used to illustrate the
  three elements necessary for fire. Each leg of
  the triangle is labeled with one of the elements
  fuel, oxygen, or heat. These three elements must
  be present at the same time for the fire to
  occur. If any one of these elements is removed
  from the fire, the fire will go out. More
  importantly, if one ingredient is missing to
  begin with, the fire will not start. Therefore,
  to extinguish a fire, it is necessary to remove
  one element, or one leg of the triangle, so to
  speak.

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Visual 1
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FIRES

• If any one of these elements is removed from the
  fire, the fire will go out. More importantly, if
  one ingredient is missing to begin with, the fire
  will not start. Therefore, to extinguish a fire,
  it is necessary to remove one element, or one leg
  of the triangle, so to speak.

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FIRES

• Removing one element from the fire is, in fact,
  the principle that underlies almost all
  firefighting methods.

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FIRES

• Fighting a fire with water removes the heat.
  Smothering the fire with noncombustible materials
  removes the oxygen. Sealing off the fire area is
  another way of removing oxygen. And loading out
  hot materials from the fire area removes the fuel.

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FIRES

• Still another way to extinguish a fire is by
  stopping the chemical reaction between the fuel
  and the oxygen. Dry chemical extinguishers
  operate on this principle. They function to
  chemically inhibit the oxidation of the fuel.
• Exactly how a fire will be fought is usually
  determined by the materials that are burning and
  the conditions in the fire area. Consequently, a
  large part of your job will be to explore the
  mine and assess the condition of the fire so that
  a decision can be made by the command center as
  to how to go about righting the fire.

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Visual 2
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Classification of Fires

• For firefighting purposes you should know the
  type of fire you are righting.
• The National Fire Protection Association
  classifies fires into the following four classes

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Classification of Fires

• Class A fires involve ordinary combustible
  materials such as wood, plastics, paper, and
  cloth. They are best extinguished by cooling with
  water or by blanketing with certain dry
  chemicals.
• Think of Class A fires as those that leave ASHES.

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Classification of Fires

• Class B fires involve flammable or combustible
  liquids such as gasoline, diesel fuel, kerosene,
  and grease. Typical Class B fires can occur where
  flammable liquids are spilled or leak out of
  mechanical equipment. They are best extinguished
  by excluding air or by special chemicals that
  affect the burning reactions.
• Think of Class B fires as those that involve
  contents that will BOIL.

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Classification of Fires

• Class C fires are electrical fires. Typical
  electrical fires include electric motors, trolley
  wire, battery equipment, battery-charging
  stations, transformers, and circuit breakers.
  They are best extinguished by non-conducting
  agents such as carbon dioxide and certain dry
  chemicals.
• If the power has been cut off to the burning
  equipment, the fire can be treated as a Class A
  or B fire.
• Think of Class C fires as those that involve
  CURRENT.

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Classification of Fires

• Class D fires involve combustible metals such as
  magnesium, titanium, zirconium, sodium, and
  potassium. Special techniques and extinguisher
  have been developed to put out these fires.
  Normal extinguisher generally should not be used
  on a Class D fire since they could make the fire
  worse.
• Class D fires are not frequently found in mines.

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Objective 2

• The team members will identify the equipment used
  in firefighting

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FIREFIGHTING EQUIPMENT

• Mines usually have a number of different types of
  equipment available for fire fighting
• o Dry chemical extinguisher
• o Water
• o High expansion foam.
• o Dry Chemical Extinguisher

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Dry chemical extinguisher

• Dry chemical extinguisher Dry chemical
  extinguisher put out fires by stopping the
  chemical reaction between the fuel and oxygen
  (which produces the flame). The dry chemical
  agents work to inactivate the intermediate
  products of the flame reaction. This results in a
  decreased combustion rate (rate of heat
  evolution) and thus extinguishes the fire.

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Dry chemical extinguisher

• There are basically two sizes of dry chemical
  extinguisher
• Hand-held extinguisher range in size from about 2
  to 55 pounds.
• Wheeled extinguisher can weigh anywhere from 75
  to 350 pounds. These extinguishers consist of a
  large nitrogen cylinder, a dry chemical chamber,
  and a hose with an operating valve at the nozzle.

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Dry chemical extinguisher

• It is generally recommended that mine rescue
  teams use multi-purpose dry chemical
  extinguisher, which contain monoammonium
  phosphate, because they are effective on Class A,
  B. or C fires. Consequently, having monoammonium
  phosphate extinguisher eliminates the teams need
  for a separate extinguisher for each class of
  fire that may be encountered underground.

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Visual 3
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Visual 3
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How to Use Hand-Held Extinguisher

• Before using any type of hand-held extinguisher
  you should be sure to check the label on the side
  of the extinguisher to make sure you're going to
  use the right extinguisher for the fire you'll be
  righting. Using the wrong type of extinguisher
  could result in a spreading fire rather than an
  extinguished fire.

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How to Use Hand-Held Extinguisher

• Also on the extinguisher label is information
  regarding the distance from the fire in which the
  extinguisher is effective. Most small dry
  chemical extinguishers are effective 5 to 8 feet
  from the fire. Larger units have ranges of 5 to
  20 feet from the fire.

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How to Use Hand-Held Extinguisher

• Using an extinguisher that is effective for only
  5 to 8 feet while standing 10 to 15 feet away
  from the fire will not put out the fire and may
  waste both valuable time and the contents of the
  extinguisher.

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How to Use Hand-Held Extinguisher

• To operate a hand-held extinguisher, you should
  grasp it firmly and approach the fire from the
  intake airside, holding the nozzle downward at a
  45-degree angle. You should stay low to avoid any
  rollback of the flames and try to get within 6 to
  8 feet of the fire before turning on the fire
  extinguisher.

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How to Use Hand-Held Extinguisher

• To effectively and quickly put out the fire, you
  should, direct the stream of dry chemical to
  about 6 inches ahead of the flame edge.

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How to Use Hand-Held Extinguisher

• You should begin far enough away to allow the
  discharge stream to fan out and you should use a
  deliberate side-to-side motion as you cover the
  fire with the dry chemical. Each sweep of the
  chemical should be slightly wider than the near
  edge of the fire.

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How to Use Hand-Held Extinguisher

• As you put out the fire closest to you, you
  should advance slowly toward the fire, forcing it
  back. And you should always be on the alert for
  possible re-ignition of the fire even though it
  appears to have been extinguished.

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How to Use Hand-Held Extinguisher

• The discharge time of hand-held extinguishers
  varies from 8 to 60 seconds, depending on the
  size and type of fife extinguisher. A 30-pound
  extinguisher will normally last 18 to 25 seconds.

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How to Use Hand-Held Extinguisher

• Also, as a safeguard, you should always be sure
  to maintain control of the extinguisher. If you
  lose control of the extinguisher you could end up
  exposing other people to the dry chemical stream.

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P-A-S-S

• Its easy to remember how to use a fire
  extinguisher if you can remember the acronym
  PASS, which stands for
• Pull
• Aim
• Squeeze
• Sweep

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P Pull the Pin

• This will allow you to discharge the extinguisher

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A Aim at the base of the fire

• If you aim at the flames (which is frequently the
  temptation), the extinguishing agent will fly
  right through and do no good. You want to hit the
  fuel

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S Squeeze the top handle or lever

• This depresses a button that releases the
  pressurized extinguishing agent in the fire
  extinguisher.

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S Sweep from side to side

• Sweep from side to side until the fire is
  completely out. Start using the extinguisher from
  a safe distance away, then move forward. Once the
  fire is out, keep an eye on the area in case it
  re-ignites.

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Using on an Obstacle Fire

• If you encounter an obstacle fire with flaming
  equipment at its center, two people using
  hand-held extinguisher should fight the fire. It
  is difficult and sometimes impossible for one
  person to put out this type of fire.

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Using on an Obstacle Fire

• The two fire fighters should approach the fire
  together from the intake airside, holding the
  extinguisher nozzle downward at a 45-degree
  angle. Both streams of dry chemical should be
  directed to 6 inches ahead of the flame edge.

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Using on an Obstacle Fire

• The two firefighters should split up and slowly
  advance around each side of the obstacle, trying
  to keep up with each other as much as possible.
  Each person should cover two-thirds of the fire
  area, using a side-to-side sweeping motion.

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Using on an Obstacle Fire

• When the fire appears to be extinguished, both
  firefighters should remain on the alert for a
  short time just in case the fire re-ignites.

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How to Use Wheeled Extinguishers

• To operate the wheeled extinguisher, you must
  first open the valve on the nitrogen cylinder.
  This forces the dry chemical through the hose to
  the nozzle. You then control the discharge from
  the base by adjusting the nozzle-operating valve

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How to Use Wheeled Extinguishers

• The method for approaching the fire and putting
  it out is the same as the method used with the
  hand-held extinguisher You should use a sweeping
  motion and direct the dry chemical stream to
  about 6 inches ahead of the flame edge.

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Water

• Water, as is commonly known, can also be used to
  put out fires. Water acts to cool the fire,
  removing heat from the fire triangle. Water is an
  effective extinguishing agent on Class A Fires.
• In most mines, the water needed to right
  underground fires can be provided by two sources
  waterlines and fire cars.

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Waterlines

• Waterlines are used in most mines and are
  available for firefighting purposes. In mines
  with shaft stations, waterline outlets located at
  the stations are required to have at least one
  fitting suitably located for, and capable of,
  immediate connection to firefighting equipment.
• If you are going to fight a Class A fire, and a
  waterline is available, you can simply hook up
  the fire hose to the waterline.

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Visual 4
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Fire Cars

• Fire cars (or water cars or chemical cars) are
  available in some mines. They may be mounted on
  tires or flanged wheels and can be pushed or
  pulled to the fire area.
• The components of a fire car can vary from a
  water tank, pump, and hose to a more elaborate
  version that contains a wider selection of fire
  fighting equipment such as water, large chemical
  extinguishers, hand tools and brattice cloth.

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Fire Cars with Low Expansion Foam

• Some fire cars contain a foam agent that can be
  hooked up to the water hose along with a special
  foam nozzle to produce a low expansion foam. The
  foam works to extinguish the fire by
  simultaneously smothering and cooling it.
• Low expansion foam is very wet and heavy. It does
  not move down a passageway as high expansion foam
  would.

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Fire Cars with Low Expansion Foam

• Low expansion foam can only be used when you're
  close enough to a fire to force the foam directly
  onto the fire

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Techniques of Applying Water to Fires

• The best way to fight a fire with water is to aim
  the water stream directly at the burning
  material.
• You should use a side-to-side sweeping motion to
  wet the entire burning surface. And, where
  possible, you should break apart and soak any
  deep-seated fires and stand by to extinguish any
  remaining embers.

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Techniques of Applying Water to Fires

• Several different kinds of water nozzles are
  available for the hose. Some produce a solid
  stream of water, some produce a fog spray, and
  others are adjustable, much like a garden hose
  nozzle, to produce a solid stream or a spray.
• Solid stream nozzles are best to use when it is
  necessary to project the water a long distance to
  the fire.
• For shorter distances, a fog spray is better to
  use on a fire because it usually will extinguish
  a fire more quickly than a solid stream.

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High Expansion Foam

• High expansion foam is used mainly to contain and
  control fire by removing two legs of the fire
  triangle oxygen and heat. The tremendous volume
  of the foam acts to smother and cool the fire at
  the same time.
• Foam is useful only in righting Class A or B
  fires. Because the foam is light and resilient it
  can travel long distances to a fire without
  breaking down.

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High Expansion Foam

• Consequently, it is very effective and used most
  commonly in controlling stubborn localized fires
  that cannot be approached at a close range
  because there is too much heat or smoke or the
  fire is spreading too rapidly.
• When using foam, firefighters can be quite far
  from the actual Tire. Five hundred feet is a
  common distance, although there have been
  successes in the past where foam was used from
  more than 1500 feet away from the fire.

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High Expansion Foam

• High expansion foam is normally used just to
  control a fire. Once conditions permit, teams are
  usually sent in to fight the fire more directly.
• It is generally recommended that teams do not
  travel through foam-filled areas. Consequently,
  before entering such an area, teams should clear
  the foam as much as possible. One way of doing
  this is to use a solid stream of water to knock
  the foam down and clear the area.

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Visual 5
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Visual 5
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Foam Generators

• Mixing water, air, and a foam concentrate or
  detergent in a foam generator makes the high
  expansion foam.

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Foam Generators

• Foam generators are portable and come in
  different sizes with different foam-producing
  capacities. The smaller models may be
  hand-carried by two people or wheeled into
  position. Other models that are larger may be
  mounted on rubber tires or may be transported on
  a track-mounted mine car.
• There are water-driven models of foam generators
  and electric or diesel-powered models. In the
  water-driven models, the foam is produced as the
  water/detergent mixture is pushed by water
  pressure through nylon netting or a screen. With
  the other models, a blower fan is used to produce
  the bubbles and push them out.

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How to Use a Foam Generator

• There are a couple different methods of using
  foam to fight a fire. With one method, the foam
  generator is positioned near the fire, and
  plastic tubing is attached to the foam outlet.
  The plastic tubing is designed to unroll as the
  foam passes through it, leading the foam directly
  to the fire area.
• Another method is to first create a confined area
  so that the foam can be pumped onto the fire to
  completely rill or plug the fire area. This is
  done by building a bulkhead with an opening in it
  for the foam generator to fit into.

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How to Use a Foam Generator

• The foam generator is then set up at the opening
  and braced or fastened down if possible. Once it
  is set up, the generator can be started and foam
  will begin filling the area. Sometimes plastic
  tubing is attached to the foam generator to
  direct the foam to the fire area.
• In some situations, a team can use the generator
  in stages, moving it closer to the fire as the
  fire is brought under control. Remember though,
  that before you can travel through a foam-filled
  area, you should knock down the foam with water
  to clear a path for you to safely walk along.

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Review Questions

• 1. Discuss the characteristics of the four
  classes of fires and what extinguishing agents
  should be used when fighting each of them.

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Answers Review Questions

• 1. Discuss the characteristics of the four
  classes of fires and what extinguishing agents
  should be used when fighting each of them.
• a. Class A fires are those that involve ordinary
  combustible materials such as wood, plastic,
  paper, and cloth. Cooling with water or
  blanketing with certain dry chemicals best
  extinguishes them.
• b. Class B fires are those that involve flammable
  or combustible liquids such as gasoline, diesel
  fuel, kerosene, and grease. They are best
  extinguished by excluding air or by special
  chemicals that affect the burning reaction.
• c. Class C fires are electrical fires. They are
  extinguished by nonconducting extinguishing
  agents such as carbon dioxide and certain dry
  chemicals.
• d. Class D fires are those that involve
  combustible metals such as magnesium, titanium,
  zirconium, sodium, and potassium. They are
  extinguished by special extinguishing agents,
  designed for such applications.

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Review Questions

• 2. Discuss each piece of equipment normally
  available to fight underground fires at the teams
  mine.

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Answers Review Questions

• 2. Discuss each piece of equipment normally
  available to fight underground fires at the teams
  mine.
• a. Hand-held extinguishers - type, location. How
  to operate the particular brand the team uses.
• b. Wheeled extinguishers - type, location. How to
  operate.
• c. Fire cars - location, what equipment is on
  car, how to operate.
• d. Waterlines - hose location, how to operate.
• e. Foam machine - location, how to operate.
• f. Any other equipment the team uses

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FIREFIGHTING Before Going Underground

• When a team goes into a mine to explore for a
  fire or to fight a fire, it should be concerned
  with two main things - spreading of the fire and
  the possibility of an explosion.
• Before going underground, the team should make
  sure that the main fan is running, that a guard
  is monitoring the operation of the fan, and that
  tests are being made at the main exhausts for any
  gases that may be present in the mine.

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FIREFIGHTING Before Going Underground

• It is important to monitor the levels of oxygen
  and carbon monoxide and of any explosive gases.
• Ventilation should always be continued through
  the mine during a fire in order to carry
  explosive gases and distillates away from the
  fire area and to direct the smoke, heat, and
  flames away from the team.

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FIREFIGHTING Before Going Underground

• If the main fan is off or destroyed, the command
  center will have to make careful plans before
  starting the fan. For one thing, everyone should
  be out of the mine before the fan is started.
• Before going underground, the team should also
  know about any possible ignition sources that may
  exist in the affected area, such as
  battery-operated or diesel equipment.

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FIREFIGHTING Before Going Underground

• Also, if there are any underground storage areas
  for explosives, oil and grease, or oxygen or
  acetylene cylinders in or near the affected area,
  you should know about them.

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FIREFIGHTING Before Going Underground

• If there is electrical power to the affected area
  of the mine, it is usually recommended that it he
  cut off. Arcing from damaged cables is a possible
  ignition source for further fires or explosions.

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FIREFIGHTING Before Going Underground

• However, if the power is cut, the mine will lose
  power to any auxiliary fans or booster fans
  underground. You will also lose power to any
  other electrically powered equipment, such as a
  pump, in the area. Losing a pump could result in
  major flooding. There are all factors that the
  command center will have to take into
  consideration when deciding about cutting the
  power.

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FIREFIGHTING Before Going Underground

• Most of this information should be available to
  the team at the time of your briefing. However,
  some of the very specific information about what
  is in or near the affected area and the
  exploration teams can only determine whether
  equipment has been left energized as they advance.

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FIREFIGHTING Before Going Underground

• Also, for health and safety reasons, it's a good
  idea prior to firefighting and immediately after
  for each team member to have a carboxi-hemoglobin
  test to determine how much carbon monoxide (CO)
  is in his or her bloodstream.

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FIREFIGHTING Before Going Underground

• Each team members on-site CO rate should then be
  compared to his or her base rate obtained
  annually during each persons physical
  examination to see if dangerous levels are
  present. If a team member has absorbed too much
  CO, he or she should not he permitted to re-enter
  the mine until the CO level is reduced.

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Objective 3

• The team members will identify the proper
  procedures for locating and assessing a mine fire

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Locating Fires and Assessing Conditions

• Two of the main objectives of exploration work
  during a mine fire are locating the fire and
  assessing the conditions in and near the fire
  area.
• Once the conditions are known and reported to the
  command center, the officials there can then
  decide how the fire should be fought.

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Locating Fires and Assessing Conditions

• The command center will want to have as much
  information as possible about the fire
• o where it is,
• o what's burning,
• o how large it is,
• o and what the conditions are near the fire area.

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Locating Fires and Assessing Conditions

• Before you enter the mine, there might already be
  some information about where the fire is located.
  The first report of a fire will often have been
  from miners working near the fire area. They may
  have reported seeing smoke and/or flames before
  evacuating the mine. These reports will help you
  to pinpoint the location of the fire and may help
  to determine the magnitude of the fire.
• Carbon monoxide and/or smoke coming from the main
  fan or main exhaust are obvious indications that
  a fire exists.

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Locating Fires and Assessing Conditions

• Lab analysis of air samples from the main fan or
  exhaust will give an accurate analysis of the
  gases that are present and help provide
  information on what is burning. The amount of
  carbon monoxide found in the sample gives some
  indication of the magnitude of the fire.

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Locating Fires and Assessing Conditions

• There is some information, however, that can be
  obtained by rescue teams during exploration of
  the mine.
• The teams can roughly pinpoint an un-located fire
  and assess its magnitude by reporting where and
  how heavy the smoke is and by feeling bulkheads
  and doors for heat.

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Locating Fires and Assessing Conditions

• If you encounter a small fire during exploration
  of the mine, you should be able to extinguish it
  immediately by using hand-held fire extinguishers
  or water from a waterline if it is nearby.
  Dealing with larger fires, however, will require
  more equipment and careful planning.
• During your exploration of the mine you must
  gather as much information as possible about the
  conditions in or near the fire area. As the
  information is gathered, it should be reported to
  the command center as soon as possible in order
  to keep the officials up-to-date with what you
  have observed.

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Locating Fires and Assessing Conditions

• You must take gas readings in the exhausts near
  the fire area to determine if the mine atmosphere
  is potentially explosive.
• Also, some damage to ventilation controls should
  be expected during a fire in the mine so you'll
  have to be especially aware of their condition.

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Locating Fires and Assessing Conditions

• And you will have to carefully check the ground
  conditions in the fire area because heat from a
  fire can weaken the back and sides.
• From all this information, the command center
  will have a fairly good indication of where and
  how large the fire is. The officials will then be
  able to decide how to go about controlling or
  extinguishing the fire whether to fight it
  directly or indirectly by sealing the mine.

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Objective 4

• The team members will identify and demonstrate
  the proper technique for fighting a fire direct

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Direct Firefighting

• Fighting a fire "directly" means that an
  extinguishing agent is put directly onto the fire
  to put it out. This usually means that the
  firefighters will have to get relatively close to
  the fire in order to use fire extinguishers,
  water, or foam on the fire.
• When fighting a fire directly, you should always
  approach the fire and fight it from the intake
  airside if possible. This will ensure that the
  smoke and heat will be directed away from you.

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Visual 6
86
Direct Firefighting

• If, however, the fire begins to back up against
  the intake air in search of oxygen, you can put
  up a "transverse" brattice (or hurdle brattice)
  from side to side leaving an open space at the
  top). This will cause increased airflow at the
  back and should slow down the progress of smoke
  and flame into the intake air current.
• The brattice should cover about one-half to
  two-thirds of the area from the floor to the
  back. You don't want to run the brattice too
  high or it will cut off airflow over the fire,
  which could result in an explosion.

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Direct Firefighting

• If heat, smoke, and ventilating air currents
  permit, water is the most desirable and efficient
  means of fighting a fire, provided it is not an
  electrical fire. Of course to fight a fire with
  water there must be a sufficient supply of water,
  sufficient water pressure, and available lengths
  of hose to reach the fire.
• In situations where the team finds it impossible
  to approach the fire for direct firefighting,
  foam or water can be pushed over the fire area to
  slow down the fire sufficiently. This will then
  allow the team to get closer to the fire to right
  it more directly.

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Visual 7
89
Hazards of Direct Firefighting

• During direct firefighting, there are certain
  hazards to the team, which you should be aware
  of. These hazards include
• Electrocution
• toxic and asphyxiating gases
• oxygen deficiency
• explosive gases
• and heat, smoke, and steam.

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Electric Shock and Electrocution

• Electric shock and electrocution are hazards to
  firefighters using water, foam, or other
  conductive agent to right a fire. For this
  reason, it is usually recommended that the power
  to the fire area should be cut off regardless of
  the type of fire. This is done not only to
  eliminate the electrical hazard but also to cut
  the power to any electrical components that may
  be involved in the fire.

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Visual 8
92
Toxic and Asphyxiating Gases

• The extremely toxic gas, carbon monoxide, is
  produced by all fires because of the incomplete
  combustion of carbon materials during the burning
  process.
• Carbon dioxide is also produced by fires, though
  it is a product of complete combustion. Carbon
  dioxide is an asphyxiant. Breathing large amounts
  of carbon dioxide causes rapid breathing and
  insufficient intake of oxygen. Too much of it in
  the bloodstream can cause loss of consciousness
  and even death.

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Toxic and Asphyxiating Gases

• Other gases such as hydrogen sulfide are even
  more toxic than carbon monoxide. Some toxic
  gases are produced by burning rubber, neoprene,
  or polyvinyl chloride (PVC). These materials are
  frequently found in electrical cables, conveyor
  belts, or tires on machinery. Even small fires
  that involve burning rubber, neoprene, or PVC can
  be extremely toxic.
• Because all of these gases can harm you, it is
  extremely important that you wear your breathing
  apparatus at all times when dealing with
  underground fires.

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Visual 7
95
Oxygen Deficiency

• Also, because fire consumes such large quantities
  of oxygen, there is a hazard of oxygen-deficient
  air in the mine-another reason for you to wear
  your breathing apparatus when dealing with mine
  fires.

96
Explosive Gases

• The buildup of explosive gases, such as hydrogen
  and methane are very real hazards for teams
  during direct firefighting. That is why it is so
  important to maintain a sufficient and consistent
  flow of air over the fire area.
• Methane is a highly explosive gas. Its explosive
  range is 5 to 15 percent when there is at least
  12.1 percent oxygen present.

97
Explosive Gases

• Hydrogen is also highly explosive in mine
  atmospheres. Its explosive range is 4.0 to 74.2
  percent when there is at least 5 percent oxygen
  present.
• Hydrogen is produced by the incomplete combustion
  of carbon materials during fires. Additionally,
  hydrogen can be liberated when water or steam
  comes in contact with hot carbon materials. This
  situation occurs when water, water mist, or foam
  is used to fight fires.

98
Explosive Gases

• Small hydrogen explosions, known as hydrogen
  "pops," are fairly common in firefighting. The
  bigger hazard with hydrogen is the possibility of
  it accumulating to a large enough extent to cause
  a violent explosion.
• Adequate ventilation over the fire area will help
  prevent the buildup of these and other explosive
  gases. If the fan slows down or stops, teams
  should immediately leave the fire area. If the
  fan continues to run slowly or remains stopped,
  teams and other underground personal should leave
  the mine entirely before the fan is restarted.

99
Explosive Gases

• And, just for your information, the fan should
  never be stopped or reversed while teams are
  underground. This could force unburned
  distillates from the fire back over the fire
  area, thereby increasing the magnitude of the
  fire.
• Also, for your own information, if any explosive
  concentrations of gas are detected in the exhaust
  air of the fire, all teams and any other
  underground personnel should leave the mine
  immediately.

100
Heat, Smoke, and Steam

• Heat, smoke, and steam are other hazards to the
  team and will determine how close you can get to
  a fire and how long you can work. Working in hot,
  smoky, or steamy atmospheres can be extremely
  uncomfortable.

101
Heat, Smoke, and Steam

• Smoke not only limits your visibility but it also
  causes disorientation. Even the simple act of
  walking is more difficult because you will not be
  able to judge your position in relation to your
  surroundings as you normally do when moving. This
  lack of orientation may cause you to lose your
  sense of balance more frequently.

102
Heat, Smoke, and Steam

• Working in hot and/or steamy atmosphere will tend
  to make you more exhausted than normal and cause
  additional stress on your system, especially if
  your working hard. You should remain aware of
  these problems while youre working under these
  conditions so that you dont over do it and
  exhaust yourself.

103
Heat, Smoke, and Steam

• Another hazard of heat is that it tends to weaken
  the back in the fire area. You should therefore
  check the ground conditions near the fire area
  frequently and scale any loose material.
• Be cautioned, also, that cold water applied to
  hot rock can cause explosive fragmentation of the
  rock.

104
Heat, Smoke, and Steam

• Keep in mind during firefighting that smoke and
  steam will be less dense near the floor of the
  mine and worse near the back of the mine.
  Adequate ventilation over the fire area should
  help to carry the smoke, heat, and steam away
  from the team.

105
Visual 6
106
Heat, Smoke, and Steam

• However, as we discussed earlier, if the fire
  begins to back up against the flow of intake air
  in search of oxygen, you can put up a transverse
  brattice from side to side, leaving an open space
  near the back. This should slow down the progress
  of the smoke and flame into the intake air
  current.

107
Review Questions

• 1. Discuss why the fan should be kept running
  during underground firefighting?

108
Review Questions

• 2. Discuss a method of controlling the backup of
  a fire against a ventilating current (intake air)
  while fighting it directly

109
Review Questions

• 3. Discuss why burning conveyor belts, cable
  insulation, and tires are particularly hazardous
  to firefighters.

110
Review Questions

• 4.Discuss other hazards that the rescue team
  should consider when fighting a mine fire
  directly.

111
Answers

• 1. Discuss why the fan should be kept running
  during underground firefighting?
• a. To ensure that explosive gases and distillates
  are carried away from the fire are. This lessens
  the chance for an explosion to occur.
• b. To direct smoke, heat, and flames away from
  the team.

112
Answers

• 2. Discuss a method of controlling the backup of
  a fire against a ventilating current (intake air)
  while fighting it directly.
• A transverse brattice can be installed from side
  to side in the passageway, with open space near
  the back. This brattice forces the ventilating
  air current to the upper portion of the
  passageway and thus slows down the progress of
  smoke and flame into the intake air current.

113
Answers

• 3. Discuss why burning conveyor belts, cable
  insulation, and tires are particularly hazardous
  to firefighters
• These materials emit extremely toxic gases as the
  fire decomposes them. Many of these gases are
  much more dangerous than carbon monoxide.
  Breathing apparatus should be worn when this type
  of fire is being fought.

114
Answers

• 4. Discuss other hazards that the rescue team
  should consider when fighting a mine fire
  directly
• a. Electrocution.
• b. Toxic and asphyxiating gases.
• c. Oxygen deficiency.
• d. Explosive gases.
• e. Heat, smoke, and steam

115
Indirect Firefighting

• Sometimes fighting a fire directly is ineffective
  or not possible because of certain hazards such
  as high temperatures, bad ground, or explosive
  gases. In these cases, it may be necessary to
  fight the fire from a distance, or "indirectly,"
  by sealing the fire or by filling the fire area
  with foam, sand fill, or water. The indirect
  methods work by excluding oxygen from the fire.
  The foam or flood of water also serves to cool
  the fire
• These indirect methods allow the firefighters to
  remain a safe distance from the fire while they
  work to control and fight a large or otherwise
  unapproachable fire

116
Objective 5

• The team members will identify and demonstrate
  the proper technique for sealing a mine fire

117
Sealing Underground

• The purpose of sealing a mine fire is to contain
  the fire to a specific area and to exclude oxygen
  from the fire and eventually smother it. Sealing
  can also be done to isolate the fire so that
  normal mining operations can be resumed in other
  areas of the mine.
• Sealing mine fires underground is a complex issue
  to which no one set of procedures will apply.
  Many factors come into play that determines the
  methods used and the eventual success of the
  sealing operation.

118
Sealing Underground

• There are two types of seals temporary and
  permanent. Temporary seals are often put up
  before permanent seals are erected in order to
  seal off a fire area as quickly as possible.
  Usually permanent seals are then constructed
  outside the temporary seals to seal off the fire
  area more effectively

119
Sealing Underground

• The map symbol for seal is three straight lines
  or two straight lines with the word SEAL printed
  after them

120
Sealing Underground

• Temporary seals are built to be fairly airtight.
  They are usually constructed of brattice cloth,
  concrete blocks. or boards.
• Permanent seals are built to be much more
  substantial and more airtight than temporary
  seals. They are notched into the back, sides, and
  floor to make them as sturdy as possible so that
  they can better withstand the force of an
  explosion, if there is one.
• Permanent seals may be built with concrete blocks
  and a strong mortar. Or they can be made of
  poured concrete, wood and plaster, or sand fill.
• The officials at the command center will decide
  what types of seals to erect based on all the
  information they have concerning the fire.

121
Sealing Underground

• Some of the factors that the command center
  considers when planning to seal a fire are
• 1. The amount of explosive gases liberated in the
  mine or present in the area. The potential for
  explosion increases as the explosive gas content
  increases.
• 2. The location of the fire and the area
  involved. This determines the number of seals
  necessary and where they should be placed

122
Sealing Underground

• 3. The composition of the overlying strata. In
  some mines, the back can be greatly weakened by
  fire and heat and may be too hazardous for the
  team to work under.
• 4. The building sites for the seals. These sites
  are determined by the location of the fire, how
  fast the fire is spreading, and (the ability to
  control ventilation in the fire area, the gas
  conditions present, and the volatility of the
  material burning

123
Sealing Underground

• 5. The availability of construction materials and
  the means of transporting them to the sealing
  sites. This factor affects the type of temporary
  or permanent seal that will be built. Often times
  in urgent situations, seals, especially temporary
  seals, are built with the materials that are
  readily available.
• In short, the command center decides where,
  approximately, to build the seals, what materials
  to use, and in what order to build the seals if
  more than one is needed.

124
Sealing Underground

• As for the team's responsibilities in sealing,
  it's up to you to pick the exact site within the
  designated area for building each of the seals
  and to do a good job in constructing the seals.

125
When picking an exact site for temporary seals,
you should look for

• (1) good ground conditions and
• (2) even back and side surfaces.
• Also, when building a temporary seal, it should
  always be built far enough into the passageway to
  allow enough room and good ground outside it for
  a permanent seal to be built. If the only site
  available for sealing has bad ground conditions,
  you may have to scale it and support it with
  timbers before beginning to build the seal.

126
Temporary Seals

• As mentioned before, temporary seals can be built
  using
• o brattice cloth
• o concrete blocks
• o wood

127
Brattice Cloth Temporary Seals

• Basically there are three ways to erect brattice
  seals. With one method, the brattice, canvas, or
  plastic can be attached to the back and sides
  with nails. The surplus brattice at the bottom
  is then weighted with timbers or other available
  loose material to keep the seal closed
• The other two methods require nailing the
  brattice to a framework of posts and boards that
  are set in a solid and well-squared location.
  With one method, the brattice is cut and nailed
  to the framework and to the sides, if possible.

128
Brattice Cloth Temporary Seals

• It may be necessary to double or triple the
  thickness of the material in order to improve the
  effectiveness of the seal. To more completely
  seal the bottom, you should shovel loose material
  along the bottom of the seal.
• Although a seal of this type will allow a certain
  amount of air leakage, it is tight enough for
  most purposes and can be erected in minimum time.

129
Brattice Cloth Temporary Seals

• Where time is not a serious factor and a fairly
  tight seal is required, a more substantial
  brattice cloth seal can be erected. To build this
  seal, set posts about one foot from each side and
  one or more posts in between. Be sure to set the
  posts firmly on solid ground.
• Nail boards across the top, center, and bottom of
  the posts. The boards should extend from side to
  side and the top and bottom boards should be
  placed as near as possible to the back and floor.

130
Brattice Cloth Temporary Seals

• If the sides are irregular, short boards
  extending from the top to the centerboards and
  from the center to the bottom boards should be
  nailed along both sides of the framework. These
  boards should roughly follow the curvature of the
  sides
• A piece of brattice cloth, canvas, or plastic
  should be nailed to the boards. The material
  should be cut large enough to cover the opening,
  with a small surplus on the sides, top, and
  bottom. It may be necessary to double or triple
  the thickness of the material in order to improve
  the air tightness of the seal.

131
Brattice Cloth Temporary Seals

• To close small openings around the edges of the
  seal, small pieces of boards should be used to
  push the brattice cloth into all irregularities
  of the back, sides, and floor and should be
  nailed into place.
• To obtain maximum tightness it may be necessary
  to caulk the edges of the seal and to shovel
  loose material aping and along the bottom.
• With reasonable care, a brattice cloth seal can
  be constructed that will allow only slight
  leakage of air.

132
Concrete Block Temporary Seals

• Concrete block seals can be put up fairly rapidly
  especially if they are laid dry. To lay them dry,
  the blocks should be built up on a solid bottom,
  one layer at a time. The last layer of blocks
  should be wedged between the top of the seal and
  the back.
• Then you should caulk the edges of the seal with
  cement or other suitable caulking material. You
  should then plaster the seal with cement or other
  suitable sealing material to make it as airtight
  as possible.

133
Wood Temporary Seals

• Various kinds of boards can be used to construct
  wood seals. Usually rough boards of various
  widths and about one inch thick are used.
  However, if a tighter seal is desired, it is
  better to use tongue-and-groove boards or shiplap
  boards
• The boards should be nailed horizontally on a
  framework of side and center posts. The posts
  should be wedged inward and hitched in the
  bottom. Also, if possible, a shallow hitch should
  be dug in the back, sides, and floor, and the
  boards should be fitted snugly into the hitch as
  the seal is erected.

134
Wood Temporary Seals

• The boards can be overlapped at the center of the
  seal if they are too long to fit perfectly. This
  will eliminate having to saw the boards and will
  therefore save some time
• If you're using shiplap boards you should nail
  them onto the framework, starting from the top
  and overlapping each board as you work your way
  down.

135
Wood Temporary Seals

• After the boards have been nailed to the
  framework, the edges of the seal should be
  caulked with cement or other suitable caulking
  material.
• If rough lumber is used and sufficient brattice
  cloth is available, the entire surface of the
  seal should be covered with a layer of the cloth.
  If brattice cloth is not available, cracks and
  holes should be plastered over to make the seal
  as airtight as possible.

136
Considerations While Building Temporary Seals

• Air Sampling Tubes
• When you build the temporary seals you should
  include provisions in some of the seals for
  collecting air samples from within the sealed
  area. Pipes with valves on them are used for this
  purpose-usually quarter-inch copper tubing
  because it is light and flexible.

137
Considerations While Building Temporary Seals

• Air Sampling Tubes (continued)
• This air sample tube can be placed anywhere in
  the seal. It should extend far enough into the
  sealed area to get a good representative sample
  of the air that is close to the fire. Depending
  on the situation, this can vary from about 40 to
  100 feet. The tube can be suspended from the back
  by tying it to timbers or rock bolts.

138
Considerations While Building Temporary Seals

• Air Sampling Tubes (continued)
• The number of seals in which air sampling tubes
  should be placed will depend on the sealed area,
  the number of seals used and their positions.

139
Considerations While Building Temporary Seals

• Ventilation
• When building temporary seals, one of the most
  important things to consider is ventilation. You
  should be careful to ensure that there are no
  abrupt changes in the ventilation over the fire
  area.
• A steady flow of air must continuously move over
  the fire to carry explosive gases, distillates,
  heat, and smoke away from the fire.
• When sealing a mine fire, the only way to keep
  the air flowing over the fire area is to leave
  one intake airway and one exhaust airway unsealed
  while other airways are being sealed.

140
Considerations While Building Temporary Seals

• Ventilation
• Then, as a final step, the last intake and
  exhaust can be sealed simultaneously. This will
  enable ventilation to continue over the fire area
  until both seals are completed.

141
Considerations While Building Temporary Seals

• Ventilation
• Sometimes two teams are used to simultaneously
  seal the last intake and exhaust. In cases like
  these, the teams should be in constant
  communication between themselves or with a
  coordinator in order to synchronize the
  simultaneous construction. Usually fires are
  sealed far enough away from the fire so that the
  heat and pressure in the sealed area do not
  affect the seals
• In some cases, however, the only site available
  for sealing a fire is close to the fire area
  where the heat and smoke are very intense in the
  exhausts. As a result the mine rescue teams will
  not be able to work in the exhausts for very long.

142
Considerations While Building Temporary Seals

• Explosions
• If an explosion is likely to occur after the
  seals have been erected, arrangements should be
  made to close the last seals after all personnel
  are out of the mine. This can be done by leaving
  hinged doors (similar to drop doors) that will
  close automatically in one or more of the seals,
  usually the last intake seal to be erected.
• These doors can be temporarily held open with a
  counterbalance in the form of a perforated bucket
  filled with water. The holes in the bucket should
  be made so that sufficient time will elapse
  before the water drains from the bucket. This
  will allow time for the personnel in the mine to
  reach the surface before the door or doors close
  to complete the seals.

143
Considerations While Building Temporary Seals

• Isolation
• It is also important to isolate the sealed area
  from the mine in as many ways as possible. This
  means that all power cables and water and/or
  airlines going into the sealed area should be
  removed or severed from the sealed area. It is
  also advisable to remove a section from the track
  or any other conductors leading into the sealed
  area.

144
Considerations While Building Temporary Seals

• Permanent Seals
• A mine cannot be returned to production until the
  sealed area of the mine has been closed off with
  permanent seals. Usually, after temporary seals
  are erected, a waiting period of about 72 hours
  is recommended before beginning construction on
  permanent seals.

145
Considerations While Building Temporary Seals

• Permanent Seals (continued)
• Permanent seals are most commonly built out of
  solid concrete blocks or sand fill, though other
  material can be used. When using concrete blocks,
  mortar is used between the blocks, and the entire
  front of the seal is plastered over. Urethane
  foam may then be put around the edges to seal any
  leaks.

146
Considerations While Building Temporary Seals

• Permanent Seals (continued)
• Urethane foam is an effective sealant when used
  around the perimeter of a seal. Urethane foam,
  though, should never be applied more than an inch
  thick because of the potential for spontaneous
  combustion with greater thicknesses.

147
Considerations While Building Temporary Seals

• Permanent Seals
• When using sand fill, two bulkheads are built
  about 20 to 30 feet apart and the space between
  the bulkheads is filled with sand fill.
• All permanent seals should be well-hitched in the
  back, floor, and sides to make them as airtight
  as possible.
• The type of permanent seals used for sealing a
  mine fire depends on the materials available, the
  length of time they are to be used, the necessity
  for complete air tightness, and the strength
  required to withstand pressure or crushing.
  Sturdily built seals are a must because the
  outward pressure on the seals can be substantial
  at times.

148
Considerations While Building Permanent Seals

• Isolation
• Just as when you veal an area with temporary
  seals, when you put up permanent seals, the area
  inside the seals has to be isolated from the rest
  of the mine. This means that all cables, lines,
  or track that were removed or severed for the
  temporary seal must also be removed or severed
  for the permanent seal.
• Sometimes this work will already have been done
  for you at the time when the temporary seals were
  built, so you will not have to take care of it
  when you build the permanent seals.

149
Considerations While Building Permanent Seals

• Air Sampling Tubes
• The permanent seals must also have provisions for
  collecting air samples from within the sealed
  area, just as the temporary seals do.
• If air sample tubes were installed in the
  temporary seals, it will only be necessary to
  extend those tubes and valves to the permanent
  seals if they do not already reach.

150
Considerations While Building Permanent Seals

• Taking Air Samples
• After the fire area is sealed, it may be
  necessary to take air samples of the air that is
  behind the seal so that the quality of the air
  can be assessed.
• The ideal time to collect an air sample is when
  the sealed area is under positive pressure or
  "breathing out."
• Pressures within and without sealed areas
  generally will vary according to temperature and
  barometric changes. These differences in pressure
  are usually described as "breathing in" (negative
  pressure in sealed area), "breathing out"
  (positive pressure in sealed area), or "neutral"
  (no difference in pressure).

151
Considerations While Building Permanent Seals

• Taking Air Samples
• When you collect an air sample, if the sealed
  area is breathing out, you should let the
  pressure evacuate the air from the sealed area
  for awhile before getting the sample. This will
  assure that you, get a good representative sample
  of the air that's in the fire area, not the air
  that's right next to the seal.

152
Considerations While Building Permanent Seals

• Taking Air Samples (continued)
• If the sealed area is breathing in or neutral,
  you should use an aspirator bulb or small pump to
  evacuate enough air from the sealed areas to
  assure that you collect a good representative
  sample of the air that's in the fire area.

153
Considerations While Building Permanent Seals

• Taking Air Samples (continued)
• Sometimes, however, seals are situated so far
  away from the fire that the air near the seals
  has an altogether different composition from the
  air near the fire. In these cases, air samples
  are usually not collected at the seals because
  they would not be accurate. Instead, a 2-inch
  borehole from the surface or another level to the
  fire area can be used to obtain air samples.

154
Considerations While Building Permanent Seals

• Foaming the Fire Area
• Foam can be used indirectly on a fire in an
  attempt to bring the fire under control so that
  more direct extinguishing methods can be used. In
  these instances, the foam generator is set up a
  distance from the fire. The foam is then pumped
  down to the fire to smother and cool it.
  Sometimes it is necessary to construct a
  temporary stopping around the foam generator in
  order to create a confined area into which to
  pump the foam.
• Once conditions permit, the generator can be
  moved closer to the fire or the team members can
  move in to fight the fire directly.

155
Considerations While Building Permanent Seals

• Using Sand fill
• In mines that have sand fill available, the sand
  fill can be used to right out-of-control fires
  indirectly. It can be pumped into an enclosed
  area of the mine to entirely seal it. For
  instance, sand fill could be pumped into a stope
  from an existing line or from a borehole drilled
  from another level. This would work to smother
  the fire, but it is only used as a last resort.

156
Considerations While Building Permanent Seals

• Flooding the Mine
• Explosions are very similar to fires in terms of
  what causes them. Just as with a fire, three
  elements must be present for an explosion to
  occur fuel, oxygen, and heat (ignition). The
  fuel for an explosion can be an explosive
  concentration of a gas or mixture of gases.

157
Review Questions

• 1. Discuss reasons why a mine fire would be
  sealed rather than fought directly.

158
Review Questions

• 2. Discuss why it is recommended that the last
  intake and exhaust seals be erected and closed
  simultaneously.

159
Review Questions

• 3. Discuss why all waterlines, power cable, and
  track leading into a sealed area should be
  severed or removed before sealing a fire area.

Slide 16